CDC 3000

CDC 3800 console at the Udvar-Hazy Center of the Smithsonian National Air and Space Museum

The CDC 3000 series computers from Control Data Corporation were mid-1960s follow-ons to the CDC 1604 and CDC 924 systems. Over time, a range of machines were produced - divided into the upper-3000 series and the lower-3000 series. CDC phased out production of the 3000 series in the early 1970s. The 3000 series were the cash cows of Control Data during the 1960s; sales of these machines funded the company while the 6000 series was designed.

The upper 3000 series used a 48-bit word size. The first machine to be produced was the CDC 3600; first delivered in June 1963. First deliveries of the CDC 3400 and CDC 3800 were in December 1965. These machines were designed for scientific computing applications, however were overshadowed by the 60-bit CDC 6000 series machines when the CDC 6600 was introduced in December 1964 and delivered in 1965.

The lower 3000 series used a 24-bit word size. They were based on the earlier CDC 924 - a 24-bit version of the CDC 1604. The first lower 3000 to be released was the CDC 3200 (May 1964), followed by the smaller CDC 3100 (February 1965), and the CDC 3300 (December 1965). The final machine in the series, the CDC 3500, was released in March 1967 and used integrated circuits instead of discrete components. The 3300 and 3500 had optional relocation capabilities, floating point arithmetic, and BDP (Business + Data Processing) instructions. These machines were targeted towards business and commercial computing.

The instruction set of the upper 3000 series was composed mostly of 24-bit instructions (packed two per word), but also contained some 48-bit instructions. The lower 3000 was based on a 24-bit subset of those available on the upper 3000 systems. It was therefore possible to write programs which would run on all 3000 systems. And as these systems were based on the prior 1604 and 924 instruction sets, some backward compatibility also existed. However the systems did diverge from each other in areas such as relocation and the BDP instructions.

All 3000 series computers used magnetic-core memory. The CDC 3500 machine used the same core memory modules as used in the CDC 6000 / Cyber 70 series computers.

Contents

The lower 3000 CPU was a 24-bit architecture: instructions were 24 bits in length, as were the two operand registers A and Q. There were four index registers of 15 bits, B0 through B3, though B0 is always zero (zero when read; writes do not affect the value). There was no status (flags or condition code) register. Up to 32,768 words of core memory, 24 bits per word, could be directly addressed, and multiple banks could be switched in. Two or three memory bank configurations were the most common.

Each instruction contained six bits of opcode, one bit specifying whether indirect addressing used, two bits of index register address and fifteen bits of address.

Arithmetic was ones' complement, so there were two forms of zero: positive zero and negative zero. The A and Q register could function as a combined 48-bit register for certain arithmetic instructions. The E register had 48 bits.

Much of the basic architecture design of the 3000 series was done by Seymour Cray, then passed on to others to complete as he moved on to designing the CDC 6000 series. Several of the innovative features that made the 6600 'the first supercomputer' can be seen in prototype in the 3000 series.

The earliest operating system for the lower 3000 series was called RTS OS. However it was quickly replaced with MSOS (Mass Storage OS). The premier operating system for the CDC 3300 and CDC 3500 was called MASTER. MASTER was interrupt-driven, supported large memory, multi-tasking.

An operating system called REAL-TIME SCOPE existed for both lower- and upper-3000 systems. A disk-based version of SCOPE was eventually made available for the upper-3000 systems.

Beverly Hills Data Center - Part of the CDC Cybernet network and also a rarity for CDC - did complete bank computing for about 12 small local banks. A midpoint of the CyberNet system, it interfaced to the Los Angeles Data Center (CDC 6600). The banking accounts were acquired from Corporation for Economic, Industrial and Operations Research (C.E.I.R) - an IBM system (1401?) which was replaced with the 3300. This system had 8 or 10 CDC 854 disk drives and connected to a Burroughs model B-3000 magnetic ink character reader (MICR).

A number of CDC 3000s were installed in France, either in academic computing centers, in software companies or in the aeronautics, nuclear and oil industries.

One CDC 3300 was installed in the late 1960s in England, in Computation Research & Development Ltd, a London-based subsidiary of the civil engineering designers Freeman Fox & Partners. It was used for engineering calculations and commercial computing. It was de-commissioned in 1974.

Communist-ruled Hungary obtained a CDC 3300 machine between 1969 and 1971. It was administered by the National Academy of Sciences throughout the 1970s, mainly for running scientific computations.[1]

International Timesharing Corporation (ITS) of Chaska, Minnesota sold timesharing services using CDC 3300s. (ITS later acquired another timesharing company that used CDC 3600s, before it, in turn, was acquired by United Computing Systems of Kansas City, Missouri.)

California State University at Northridge had a dual 3170 that provided timesharing service to the California State University and College system. Many of the other campuses also had CDC 3150 machines for local batch operation. In 1970 CDC 3150s were installed at most campuses of the California State College system. San Jose State and LA State got CDC 3300s and served as regional data centers with (very flaky) data links to the other campuses. California State Polytechnic College (San Luis Obispo) and San Diego State University had IBM System/360s. The rest got 3150s. Typical configuration was 24K words of 24-bit core memory, four 7-track tape drives, drum printer, card reader, card punch, two 8MB disc drives (removable packs). At Humboldt State College where I worked this was used for both administrative and instructional purposes. It replaced an IBM 1620.

The Center for Naval Analyses had a CDC 3800 from about 1968 until about 1975. It was used for scientific computing in support of operations research for the U. S. Navy.

Other CDC 3300 systems installed in former Eastern Bloc countries (list not complete):

Computing Research Centre, Bratislava

Central Statistical Office, Prague.

Romanian Aircraft, Bucharest (3500 System)

There were many CDC 3000 series machines in Australia. CSIRO had a 3600 installed in Canberra in 1964, with satellite 3200 machines in Melbourne, Sydney, and probably Brisbane and Adelaide. The Bureau of Census and Statistics had a 3600, 3300, and a 3500 in Canberra, with a 3200 in each of the six state capitals several of which were upgraded to 3300s about 1970. Monash University had a 3200 delivered in 1964.[2] Defence Signals Directorate had at least one. BHP had two 3300 machines at each of its Newcastle and Port Kembla Data centres. They were replaced by 3500s in 1977, and remained in operation until the mid-1980s.

There was a story that Trevor (E.T.) Robinson told the CDC Headquarters that he could sell at least 15 in Australia if CDC built the lower (cheaper) 3000 series.

^Video on YouTube, Video footage taken by Ron Bird of the touchdown at Essendon Airport of the Flying Tigers CL44 Swing Tail freighter and the unloading of the CDC 3200 system at the Monash Clayton campus by Wridgway Bros, 1964.